Electromagnetic measuring instrument.



W. J. DAVIS. ELECTROMAGNETIC MEASURING INSTRUMENT.

APPLICATION FILBD J bNE 20, 1913.

Patented Jam. 5, W15.

hma m WILLIAM JEFSEIEH DAVIS. F ENFIELD, ENGLANJD. ASSEEGrI IGEt TQ ED153011" AND SWAN UNITED ELECTRIC LIGHT COMPANY LIMITED, 01 LONDQN, ENfi-LANLD.

ELTEWJLEUMAGNETIC MEASUHING INSTRUMENT.

Wuum

Application filed. June 20, 191*.

This invention relates to improvements in electromagnetic measuring instruments, such as voltmeters, ammeters and the like, of the kind wherein the instrument is made dead heat or aperiodic Without providing a separate air clamping chamber for this pun pose" By the peculiar construction and this-- position of the partsot the instrument greater sensitivonesa isohtainecl', than has hitherto been practicable, resulting n a very low Watt consumption, one giving; a un1- fertility of stole."

Accortiing to the present invention the clamninc chamber is conteineol within the coil through which the current is passccl to excite the irons in theusual ay, anol hy the repulsion hetween them'to indicate the characteristics of the current under considera t on. The moving iron etteched to the nointcr itseli constitutes the plunger-or vane for the damping chamber, anclin this way an extratdamning chamber anti plunger are rendered unnecessary anoi an economy of space and a reduction of the numborof moving parts is eli'e'cted.

An instrument embodying" my invention is illustrated in the accompanying drawings in which" Figure 1 is a front eletatimi of the in strun1ent,.l3is;. 2 a sicle elevation from the right hand side of Fig. 1, with the coil removed, Fig. 3 a section taken on line 2 $2 2 looking; to the right, Fig. ia side elevation of the moving; parts renioveol irom the rest of the instrument, and Fig 5 cletail View hereinafter referred to.

The drum upon Which the coil 0 is Wound has a hollow core a between the flanges b and c which core is substantially sector shaped externally and internally. Within the core and along; the apex of the sector lies the shaft it having one end mounted in a bearing; 6 screwed into the rear flange 5 and the other cnc]. mounted in a bracket f" secured to the front flange 0. This shaft cl carries the usual pointer g which passes over specification of Letters Itatont.

Patcisitetli Jan, ilt tht Serial hi0. Y'Mfitll.

the measuring" scale, and the sprint; It for returning); the pointer to zero, Depending from the shaft 03 is a vane t" (shown more particularly in Figs, 1, 3, t and 5) which extends almost from end to end of thelhollow core of the drum but just clears the ends. The lower edge of the vane 2 lies just clear of the inner sicle of the curved Wall of the core a, one as the shaft d lies in the apex of the sector, Whenthe shaft is rotated. the vane sweeps across the of thin iron 7 interior of the hollow core with its edge and,

ends alwaysclose to the -'Walls of the chamber containing it. The tone 6 forms one of the irons of the instrument, and; the other iron y is nreferahly'nlacecl outside the core (it. With a core of sector shaneol exterior as in the instrument illustrated, the outer iron 55' is preferably arranged. in the position shown, with one end boot up around the core, at the si le Where the inner iron rests when the pointer is at zero. '1'." he chamber containing the iron i is closed by a plate Fa secured over the opening" through which the yane is insertcai. When the instrument is excited the repulsion between the irons 2' and 7' causes the foririer toeweep across the chamber containing it, and by reason of the resistance clue to the smali air mp between the moving? vcne and the curved side of the chamber the movement of the instrument will he cleari heat. lnsteaol of the spring it a Weight may he used to return the pointer to zeroantl Fig. 5 shows aims Z, Z on the shaft ot the instrument to either of which -a Weight may he attached, according the --instrument is to he usecl with. the nointer pointing upward or downward. An adjustable Weight rW-(Fig. 2) is furnished to halonce the vane'exactly against the pointer and out the movement: in equilibrium.

Owing to the comparatively long radius from which the moving iron 2 swings exsector shaped in cross section,

formed by the winding of the coil 0 alone, but the use of a drum with a core, as described, is preferred.

' The advantages derived from the use of a segmental chamber for damping purposes are that the resistance to the vane within the segmental chamber is relatively great as compared with other forms of chambers heretofore employed, such as circular chamers. In a circular chamber the edge of thevane is not close to the wallet the chamber but must necessarily be spaced therefrom throughout the entire circumference of the vane and thus the air easily escapes about the edges of the vane behind the pivot thereof. In the segmental chamber the vane which is of corresponding shape as above described has its edge close to the inner wall of the chamber and its pivot point is located in the apex of the chamber so that air cannot easily escape about the pivotal axis of the vane.

What I claim as my invention is:

.-1. An electromagnetic measuring instrument comprising a coil having Within it a chamber of substantially sector shaped section with a vane constituting the moving iron pivoted. therein along the apex of the sector and a fixed iron lying partly along the curved sideof the sector and partly turned up along onefiat-side, around the free edge of the moving iron when in the zero position.

An electromagnetic measuring instrument comprising a hollow core having a chamber therein and being substantially a coil wound upon said core, a vane pivoted in said chamher along the apex. thereof, and constituting a moving iron, and a fixed iron located on the outside of the core and lying partly along the curved side of the sector shaped core and partly turned up along one of the flat sides thereof around the free edge of the moving iron when in zero position.

3.. An electromagnetic measuring instrument comprising a drum, flanges on the ends of said drum,- a hollow core between said flanges having a chamber therein and being of substantially sector shaped in cross section, a coil. \vound upon said core, a shaft journaled at its opposite ends and lying within said core at the apex thereof, a vane fixed upon said shaft within said chamber and constituting a. moving iron, a removable plate at one end of said core for closing the vane in said chamber, a permanent closure at the opposite end of said core for housing said vane, a pointer secured to said shaft for movement with said vane,'means for normally holding said. pointer in zero position, and a fixed iron dis1')oscd'bct\veen the core and the coil and lying partly along the curved side of the sector shaped core and being partly turned up along one fiat side of the core around the free edge of the moving iron when in zero position.

In testimony whereof I. have aflixcd my signature in presence of two witnesses.

l VILLIAM JOSEPH DAQVliS.

W'itnesses Lovnnnss' Bunnie, J, Vi. 'lHonrsoN. 

